1. Field of the Invention
The invention relates to a sewing motor driving device.
2. Description of Related Art
On a main shaft of a conventional sewing machine, a sewing machine pulley is fixed and a motor pulley is fixed on an output shaft of a sewing motor. The sewing machine and the sewing motor are connected by a belt which extends between the sewing machine pulley and the motor pulley. In sewing a thick fabric on the conventional sewing machine, the torque of the main shaft of the sewing machine is increased by reducing the working diameter of the motor pulley to enhance the penetrating force of the needle or by employing a sewing motor having an increased capacity.
The reduction of the working diameter of the motor pulley, to enhance the torque of the main shaft at a low sewing speed, however, entails a reduction in the maximum sewing speed. The employment of a sewing motor of a high rated power increases the cost of the sewing machine.